342 mr. darwin's hypothesis. 



•ho other conjecture respecting them than that they 

 had been produced under water, and raised above 

 it by the elevation of the mass on which they re- 

 posed. They looked exactly like the remnants of 

 a much larger mass that had been gradually eaten 

 away and destroyed by the action of the sea and 

 weather. 



Now all the facts which I have just now been de- 

 tailing go to shew that the north-east coast of Aus- 

 tralia has either been slightly elevated, or that it 

 has at least not suffered any depression during a long 

 period of time. Those who are familiar with Mr. 

 Darwin's hypothesis respecting coral reefs will see 

 the drift of this remark. 



This hypothesis rests upon the assumption that 

 coral- reef-forming polyps do not live at a greater 

 depth than twenty or thirty fathoms, and that, con- 

 sequently, 'coral reefs rising abruptly from unfathom- 

 able depths must necessarily have been produced 

 by the depression of the bottom of the sea. That 

 wherever we find such coral reefs, the bed of the 

 sea must have once been within twentv or thirtv 

 fathoms of the surface, that corals then grew upon it, 

 and that as the bottom was slowly depressed, the 

 corals built upwards, so as always to keep the upper 

 portion of the reef within the required depth. 



1 must refer the reader to Mr. Darwin's volume 

 on coral reefs for details on this subject, where he 

 will find a mass of materials accumulated and ar- 

 ranged with almost unexampled industry, and rea- 



